package com.hmdp.service.impl;

import cn.hutool.core.bean.BeanUtil;
import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSON;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import com.hmdp.utils.SystemConstants;
import org.springframework.data.geo.*;
import org.springframework.data.redis.connection.RedisGeoCommands;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.domain.geo.GeoReference;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringredisTemplate;

    @Override
    public Result queryById(Long id) {
        //解决缓存穿透
//        Shop shop = queryWithPassThrough(id);

        //互斥锁解决缓存击穿
//        Shop shop = queryWithMutex(id);

        //逻辑过期解决缓存击穿
        Shop shop = queryWithLogicalExpire(id);

        if (shop == null) {
            return Result.fail("店铺不存在");
        }

        return Result.ok(shop);
    }


    //设置锁
    private boolean trylock(String key){
        Boolean flag = stringredisTemplate.opsForValue().setIfAbsent(key, "1", 10L, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private void unlock(String key){
        stringredisTemplate.delete(key);
    }
    //逻辑过期时间
    public void saveShop2Redis(Long id, Long expireSeconds){
        //1,查询店铺逻辑过期时间
        Shop shop = getById(id);
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3.写入Redis
        stringredisTemplate.opsForValue().set(CACHE_SHOP_KEY+id,JSONUtil.toJsonStr(redisData));
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long shopId = shop.getId();
        if (shopId == null){
            return Result.fail("店铺id不能为空");
        }
        //1，更新数据库
        updateById(shop);
        //2.删除缓存
        stringredisTemplate.delete(CACHE_SHOP_KEY+shopId);

        return Result.ok();
    }

    @Override
    public Result queryShopByType(Integer typeId, Integer current, Double x, Double y) {
        //1.判断是否需要根据坐标查询
        if (x == null || y == null){
            //不需要坐标查询，按数据库查询
            Page<Shop> page = query()
                    .eq("type_id",typeId)
                    .page(new Page<>(current, SystemConstants.DEFAULT_PAGE_SIZE));
            //返回数据
            return Result.ok(page.getRecords());
        }
        //2.计算分页数据
        int from = (current - 1) * SystemConstants.DEFAULT_PAGE_SIZE;
        int end = current * SystemConstants.DEFAULT_PAGE_SIZE;

        //3.查询redis 按照距离排序、分页。结果：shopId distance
        String key = SHOP_GEO_KEY + typeId;
        //GEOSEARCH key BYLONLAT x y BYRADIUS 10 WITHDISTANCE
        // 使用GEORADIUS查询
        GeoResults<RedisGeoCommands.GeoLocation<String>> results = stringredisTemplate.opsForGeo()
                .radius(
                        key,
                        new Circle(new Point(x, y),
                        new Distance(5000)),
                        RedisGeoCommands.GeoRadiusCommandArgs.newGeoRadiusArgs()
                                .includeDistance()
                                .limit(end)
                );
        //4.解析出id
        if (results == null){
            return Result.ok(Collections.emptyList());
        }
        List<GeoResult<RedisGeoCommands.GeoLocation<String>>> list = results.getContent();
        if (list.size()<= from){
            //没有下一页了，结束
            return Result.ok(Collections.emptyList());
        }
        //4.1截取form ~ end 的部分
//        list().subList()
        List<Long> ids = new ArrayList<>(list.size());
        Map<String,Distance> distanceMap = new HashMap<>(list.size());
        list.stream().skip(from).forEach(result ->{
            //4.2获取店铺id
            String shopIdStr = result.getContent().getName();
            ids.add(Long.valueOf(shopIdStr));
            //4.3获取距离
            Distance distance = result.getDistance();
            distanceMap.put(shopIdStr, distance);
        });
        //5.根据id查询Shop
        String idStr = StrUtil.join(",",ids);
        List<Shop> shops = query().in("id", ids).last("ORDER BY FIELD(id," + idStr + ")").list();
        for (Shop shop : shops) {
            shop.setDistance(distanceMap.get(shop.getId().toString()).getValue());
        }
        //6.返回
        return Result.ok(shops);
    }

    //缓存穿透的代码（防止丢失）
    public Shop queryWithPassThrough(Long id){
        //1.从Redis查询商铺缓存
        String key = CACHE_SHOP_KEY + id;
        String shopjson = stringredisTemplate.opsForValue().get(key);
        //2.判断缓存存不存在
        if (StrUtil.isNotBlank(shopjson)){
            //存在，直接返回
            Shop shop= JSONUtil.toBean(shopjson, Shop.class);
            return shop;
        }
        //不存在，但有“” 和 null 两种情况， 不能让空值去查询数据库,null可以去查询数据库，空值要返回错误
        if (shopjson!=null){
            //返回一个错误的值
            return null;
        }
        //3.不存在，则根据id查询数据库
        Shop shop = getById(id);
        //4.不存在，返回错误
        if (shop == null){
            //虽然不存在，但是为了防止缓存穿透，设置空值""
            stringredisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);
            return null;
        }
        //5.存在，将商铺数据写入Redis中
        stringredisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL,TimeUnit.MINUTES);
        //6.返回
        return shop;
    }

    //缓存穿透的代码（防止丢失）
    public Shop queryWithMutex(Long id){
        //1.从Redis查询商铺缓存
        String key = CACHE_SHOP_KEY + id;
        String shopjson = stringredisTemplate.opsForValue().get(key);
        //2.判断缓存存不存在
        if (StrUtil.isNotBlank(shopjson)){
            //存在，直接返回
            Shop shop= JSONUtil.toBean(shopjson, Shop.class);
            return shop;
        }
        //不存在，但有“” 和 null 两种情况， 不能让空值去查询数据库,null可以去查询数据库，空值要返回错误
        if (shopjson!=null){
            //返回一个错误的值
            return null;
        }
        //3.不存在，则尝试获取互斥锁    （解决缓存击穿）
        //3.1， 互斥锁获取失败，则休眠一段时间并重试
        String lockkey = LOCK_SHOP_KEY + id;
        Shop shop = null;
        try {
            boolean trylock = trylock(lockkey);
            if (!trylock){
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            //3.2 则根据id查询数据库
            shop = getById(id);
            //3.3模拟重建的延迟
            Thread.sleep(200);
            //4.不存在，返回错误 （解决缓存穿透）
            if (shop == null){
                //虽然不存在，但是为了防止缓存穿透，设置空值""
                stringredisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);
                return null;
            }
            //5.存在，将商铺数据写入Redis中
            stringredisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL,TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }finally {
            //6.释放互斥锁
            unlock(lockkey);
        }
        //7.返回
        return shop;
    }

    //开启线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //逻辑过期解决缓存击穿
    public Shop queryWithLogicalExpire(Long id){
        //1.从Redis查询商铺缓存
        String key = CACHE_SHOP_KEY + id;
        String shopjson = stringredisTemplate.opsForValue().get(key);
        //2.判断缓存存不存在
        if (StrUtil.isNotBlank(shopjson)){
            //3.存在，直接返回
            Shop shop= JSONUtil.toBean(shopjson, Shop.class);
            return shop;
        }
        try {
            //4.将JSON反序列化为对象
            RedisData redisData = JSONUtil.toBean(shopjson, RedisData.class);
            JSONObject data = (JSONObject) redisData.getData();
            Shop shop = JSONUtil.toBean(data, Shop.class);
            LocalDateTime expireTime = redisData.getExpireTime();
            //5.判断缓存是否过期
            if (expireTime.isAfter(LocalDateTime.now())){
                //5.1 未过期则返回商铺信息
                return shop;
            }
            //5.2已过期，尝试获取互斥锁
            //6.缓存重建
            //6.1获得互斥锁
            String lockkey = LOCK_SHOP_KEY + id;
            boolean isLock = trylock(lockkey);
            //6.2判断是否可以获取互斥锁
            if (isLock){
                //注意，获取锁成功应该再次检测redis缓存是否过期，做DoubleCheck，如果存在则无需重建缓存
                //6.3可以获取互斥锁，开启独立线程，实现缓存重建
                CACHE_REBUILD_EXECUTOR.submit(()->{
                    //重建缓存
                    try {
                        //实际情境下正常是30分钟
                        this.saveShop2Redis(id,20L);
                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }finally {
                        //释放锁
                        unlock(lockkey);
                    }
                });
            }
            //6.4返回过期的商铺信息
            return shop;
        }catch (Exception e){
            log.error("解析RedisData对象失败",e);
            return null;
        }
    }
}
